Im breathing new life into an 84 SD. This is your standard 400 dollar diesel. So its slow, oily, and on the verge of catastrophic failure if knowone shows some lovin.


I had the vac system disconnected to fix a leaking trans modulator and when I went to shut the car off the linkage wouldn't move far enough back to shut down the engine, only take it down a few hundred rpm. This is at the stop lever. Ive taken apart the linkage, and have isolated the problem to the injection pump. Looking behind the ip, its seems to be hitting an adjustment screw (the large flat head upward facing screw). I always thought that was for idle adjustment, but it seems more like a "stop" screw for the linkage. Any ideas?



A few fyi's


The 300SD air cleaner has a larger intake. I compared it to the one on my 81 SD (84 w123 engine) and after noticing that the intake of the w123 air cleaner is significantly smaller, I promptly swapped then .

I also noticed the wastegate hose was split wide open. I took a 4 inch section of fuel line which seemed almost identicle to the old hose. Are these special rated hoses? Im guessing it gets damn hot down there. Should fuel line suffice? This is a piece i got from the return fuel flow (the po replaced a split cigar hose with an exceedingly long piece of standard fuel line (has a white line down the side of it)). I am selling this car asap, but I want the car to last regardless of if the next owner even cares, and this seems pretty critical to have working in the long run (a correctly functioning wastegate). Can replacing this hose help regain power? I wouldnt imagine, it keeps boost from going to high.



The car has a power steering leak at the pully. Seems the seal has given out. Has anyone ever heard of this happening? It seems like everythng that usually doesnt fail, is failing on this thing. Fortunatly fastlane carries this seal: http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2HF1EHC572HF1EHWED&yearid=1984@@1984&makeid=MB@@MB@@X&modelid=300-SD-002@@300SD&catid=M@@Steering&subcatid=M2080@@P%2FS+Seal&mode=PA&subcatid=M2080@@P/S%20Seal&applicationid=000031608&source=www.peachparts.com&clientid=catalog.mercedesshop

Has anyone done this repair? Seems like it may be easier to just get a pump at pick n pull (and I can get one cheap, as a friend works there). I figuer it looks good on an ebay auction when a 20+ year old car doesnt leak a single drop of anything..

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1981 300SD 512k OM603

Also the 84 SD has a switch under the hood that makes contact when the hoods closed. Located by the battery/monovalve. Any ideas? There is no aftermarket under hood light installed or anything. if its not for a light, what is it?

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1981 300SD 512k OM603

I too have seen this apparent hood light switch located close to center at the fire wall on my 85 - a little light would be a nice addition especially in case of emergency repairs without flash light.

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1985 300D, 250k
1980 300SD, 180K

Maybe the switch is there to tell you if the hood is not closed completely. Someone with an owners manual may be able to tell you.

There are several Threads concerning changing the seal/rebuilding of the power steering pumps. In one of the threads someone mentioned there is more than 1 size of seal that goes on those pumps.
Also the free loaned out Pulley Removal tool form the Auto Part places may not work on the Power Steering Pump Pulley.

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84 300D, 82 Volvo 244Gl Diesel

That switch is actually is the Alarm system if someone opens the hood with all of the door locked or alarm activated the alarm will go off...

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Current Garage
2008 Mercedes GL320 CDI 188k mi Repair/Work in progress
1994 S350 160k mi Garage Queen & prepping for repairs
2005 E320 CDI 203k mi Healthy & Daily Driver
1994 S350 357k mi Retried as parts car
1984 300TD 214k mi Blown OM617 Poss OM603 Swap??

Sold
1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi
15+ Others that has come, stay and gone

GONE, BUT NOT FORGOTTEN
1995 E320 SE 220k mi
1984 300SD 350k mi

Ive even found another alarm switch behind the instrument cluster








So PS pump seals are available, but there's two different sizes? Or is it just a year thing..

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1981 300SD 512k OM603

i went to the dealer to order a ZF pump front seal and to the clerks amazement, it was instock. ill keep you guys posted on the seal replacement

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1981 300SD 512k OM603

Well I have the seal in and the pump is back together and installed. its not a difficult repair at all, just be careful to remember how the pump goes back together. The "vanes" are also direction sensitive and the shiny side should be facing outward. pretty amazing how this thing works!

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1981 300SD 512k OM603

It could be that the Vanes have worn into that shape; as you said keep them in the same position and place that each Vane came from.

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84 300D, 82 Volvo 244Gl Diesel

It's for the alarm system.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)